In his lengthy and interesting blog post covering the future of Plasma, KDE's Aaron Seigo proposes Qt Quick and QML (a declarative language that embeds JavaScript) as replacement of the Graphics View architecture currently used by Plasma. This holds a promise of massive speedups and cheap effects as all paint operations become candidates for OpenGL acceleration, contrary to the aging Graphics View architecture that is still stuck with various inefficiencies caused by the underlying QPainter approach. Expressiveness and easy programmability of QML is a nice bonus, of course.

I agree with many of your concerns, however the duke nukem comparison is out of line. There is a huge difference between vaporware that never gets released, and software that is continuously improved and released.

Kde 4 today works great ... when it works. When it doesn't work, it doesn't work too well. I wouldn't describe it as unstable, maybe just less stable than other desktop environments. Part of that is just the maturity of the code base. It also concerns me that the existing core is being changed, but it sounds like a lot of the framework will remain intact. Maybe it won't be that much of a change, but it still has the possibility of removing focus from the small tweaks and bug fixes to the deeper changes.